This is a proposal to pool data from 12 major prospective studies on diet and coronary heart disease that have used a comprehensive assessment of diet. The overall objective of the proposed investigation is to quantify the role of dietary factors in the etiology of coronary heart disease. Specific hypotheses include an adverse effect of saturated fat and carotenoids (alpha-carotene, lutein, and lycopene), flavonoids, folic acid, and vitamin B6. Plausible biological interactions between nutrients, such as fatty acids of the n-6 and n-3 series will also be explored. Each participating center will send data on tape to the coordinating unit at the Department of Nutrition, Harvard School of Public Health. The relations of dietary factors and coronary heart disease will first be estimated within each study and compared for consistency. Data will then be combined to obtain the best overall estimates, taking into account the validity of dietary data collected at each center. Members from study centers will meet annually to discuss the interpretation of findings. Over 6,000 cases of myocardial infarction or coronary death are anticipated, which will provide excellent precision in measuring associations, and will allow the comparison of extremes of intakes that are poorly represented in individual studies. The proposed investigation is a highly cost-effective way of advancing knowledge on diet and coronary heart disease (CHD) because it draws on a large amount of data already collected and will take advantage of the expertise and software developed for a similar project on breast cancer.